1. Field of the Invention
The present invention relates to a mobile radio communication terminal such as a mobile station and a portable information terminal, and in particular, to a mobile radio communication terminal for selectively using a plurality of radio communication systems to perform radio communication.
2. Description of the Related Art
In recent years, with the development of radio communication technologies and an increase in communication needs, a variety of mobile radio communication terminals have been developed and used. Among these terminals are terminals which allow communication by selectively using a plurality of radio communication systems.
For example, a terminal which selectively uses the TDMA (Time Division Multiple Access) system and the AMPS system, one type of the FDMA (Advanced Mobile Phone System) system, a terminal which selectively uses the PDC (Personal Digital Cellular) system, one type of the TDMA system and the PHS (Personal Handyphone System), and a terminal which selectively uses the CDMA system and the FDMA system are known. Recently, a terminal which selectively uses the W-CDMA (Wideband-Code Division Multiple Access) system and the BT (Bluetooth) system, one of the short-range radio communication standards using the ISM (Industry Science Medical) band has been devised.
However, a terminal of this type conventionally used or devised has a disadvantage that such a terminal has large power consumption because it is generally equipped with circuits each of which is dedicated for each radio communication system, and has considerably shorter battery life than apparatus using a single radio communication system alone. Such a terminal must be provided with a power supply circuit having large power capacity for simultaneous use of a plurality of radio communication systems and thus the terminal had to employ a large-sized power supply circuit as well as large-sized apparatus to prevent overheating.